# Cancer

Uncontrolled cell division caused by mutations in genes that control the cycle. Proto-oncogenes (accelerators) mutated into oncogenes are stuck on. Tumour suppressor genes (brakes) such as p53 are switched off.

Biology (university) · Part 06: Cell cycle, mitosis and meiosis · Card 5 of 8 · Last updated 2026-10-19

## Analogy

A car with a stuck accelerator and broken brakes.

## In practice

Several mutations are usually needed, which is why cancer risk rises with age.

## Practice

### Flashcards

- **What is the difference between an oncogene and a tumour suppressor?** An oncogene is a stuck accelerator. A tumour suppressor is a brake that has been lost.

### Interview questions

**Explain how checkpoints control the cell cycle and what happens when the control fails.**

- Checkpoints at G1, G2 and M
- Cyclins and CDKs drive progress
- p53 stops damaged cells
- Mutation in brakes or accelerators leads to cancer

## Questions people ask

### What is the difference between benign and malignant tumours?

A benign tumour stays in one place and is usually enclosed, so it can often be removed. A malignant tumour invades nearby tissue and can spread through blood or lymph to other organs, called metastasis. Metastasis is what makes cancer hardest to treat.

### Why does cancer risk increase with age?

Cancer usually needs several mutations in different cell-cycle genes. These build up slowly over many cell divisions and with exposure to damage from the environment, such as ultraviolet light and tobacco smoke. The longer someone lives, the more chances there are for the full set of mutations to occur.

## Related concepts

- [Cell cycle](https://studyvisually.com/learn/science/biology-university/biology-university-part-6/biology-university-part-6-concept-1)
- [Cell cycle checkpoint](https://studyvisually.com/learn/science/biology-university/biology-university-part-6/biology-university-part-6-concept-2)
- [Mitosis](https://studyvisually.com/learn/science/biology-university/biology-university-part-6/biology-university-part-6-concept-3)
- [Cytokinesis](https://studyvisually.com/learn/science/biology-university/biology-university-part-6/biology-university-part-6-concept-4)

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